Apparatus for measuring and recording oscillating pressures, particularly blood pressure



April 25, 1950 F. A. E. SERRELL 7 2,505,436 APPARATUS FOR MEASURING AND RECORDING OSCILLATING PRESSURES, PARTICULARLY BLOOD PRESSURE 4 Sheets-Sheet 1 Filed Sept. 24, 1946 3 R, R a

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April 25, 1950 F. A. E. SERRELL 2,505,436

APPARATUS FOR MEASURING AND RECORDING OSCILLATING PRESSURES, PARTICULARLY BLOOD PRESSURE 4 Sheets-Sheet 2 Filed Sept. 24. 1946 if/vue/vro B Uk-MMQM Apnl 25. 1950 F. A. E. SERRELL 2,505,436

APPARATUS FOR MEASURING AND RECORDING OSCILLATING PRESSURES, PARTICULARLY BLOOD PRESSURE Filed Sept. 24', 1946 4 Sheets-Sheet 3 1nd. osc.

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-lllTll111 lllllill llllllllllllllllllllII V MM Fig. 4 is a sphygmogram recorded by the appa ratus, with times in abscissae and th ordinates in proportion to oscillometric indications.

Fig. 5 is a perspective detail of the mirror assembly.

Figs. 6 and 7 are sections on an enlarged scale of a stop-cock and a. valve.

The frame-work l of the apparatus carries screen 2. This is a glass plate having its inside face covered with a material which remains phosphorescent for a certain time when exposed to short luminous waves. Readings are made on the outside face by transparency.

Under the screen in a dark box at the forepart of the irame-work is a mercury vapour lamp 3. Through a double diaphragm light is thrown solely on the spot mirror.

This spot mirror 5, in turn, throws a spot light on the screen 2.

An air-tight box 6 at the rear of apparatus has a transparent curved surface l. Box 6 is secured on frame-work by screws 8 and air-tight butt-joint Q.

Mirror 5 is held on horizontal shaft it by lugs Illa (Fig. 5). It oscillates around this shaft in a round frame 5 i, which in turn is supported by a shaft 13 and held by a point ended screw [2. Shaft l3 revolves with frame i l on a sup-port I i, fastened within box 6 by two small posts It and I5.

The lower end of shaft I3 is fast with a short lever 16 shown perpendicularly to the plane of Fig. 1.

This lever is connected to a crank lever it through a tension spring i9 and a rod ll which is pointed at both ends and lies in abutting relationship with levers I6 and 18, providing a spacer therebetween.

A crank lever 2i) which revolves with shaft 2| carries lever 58 through pivots 22 and 22. The lower branch of lever i8 rests in sensitive contact with the centre of a manometric capsule 24 through knife-shaped support 23 and spring 25.

Capsule 2 is fastened on plate 2%. Proper adjustment in vertical and horizontal position of fixture of this plate it with respect to the bottom of box it is ensured by screws 2? and 28, (the latter accessible from outside by unscrewing and taking oif a screw-threaded plug 28a) and spring 29. Adjustment of screw 28 modifies leverage of amplitude of motion of the spot mirror as a function of the deformations of capsule 24.

Thrust rod 35 bears on spiral cam 3| at one end and on crank lever 32 fastened on shaft 2| at the other end, and proper contact of moving parts is ensured by spring 33.

Movement of lever I8 and consequently movement of frame i I and mirror around axis l2i3 can therefore be the result either of a movement of thrust rod 3? knife 23 providing a. fulcrum, or of variations in size of capsule 24, in which case the fulcrum is provided by pivots 22. Shaft S i supported in bearings 35 and 35 carries besides cam 3| two other cams 36 and 31 actuating electrical contacts 38 and 39.

This shaft 35 is revolved by synchronous-motor 40 at a reduced speed of about one revolution in ten seconds, through a worm ll and a worm wheel 42.

In the invention as thus far described, it is readily seen that movements of the spot mirror about the axes of pivots I2, 13 are subjugated with precise and fine sensitiveness on the one hand to deformation of capsule 24 and on the other hand to rotation of motor 40.

In addition to this, further movements of the spot mirror about the axis of pin It depend on deformations of capsules 4a in the fo.lowing manner:

A very supple thread 43 is fastened at one end to the upper back part of the mirror at 135; (Fig. 5) and at the other end to the centre of capsule as. Said thread passes between shaft ii) and back of mirror 5, preferably in a groove ltb on shaft iii and in line with point i2 and pivot [3 of frame ll.

Another supple thread 45 is fastened at one end to the lower back part of mirror 5 and passes in same groove as thread 43. The other end is attached to an end of a spring 36 the other end oi which is attached to the lug in which screw I2 is supported, as shown; the function of spring it which through thread 35 tends to rotate mirror 5 counterclockwise (Fig. 1) is to maintain threads t3, t5 permanently in stretched condition. It is further desirable to connect thread :33 to capsule as through a rather stiff spring 65 as this avoids breaking of threads that might be due to great deformations of capsules 34, whether normal or accidental. Capsules it are fastened to plate 4? which, same as part 26 is connected to the bottom of box 6, by screw 48. Suitable position of mirror is also controlled by screw as (accessible from outside after unscrewing and taking ed a screwthreaded plug 69a) and spring Air tight box 6 containing the capsules can be connected to a compressed air tank 5! filled through ingress pipe 52. The stop cock 533, remote controlled by iiexiole rod 5d and knob 54a, sends compressed air in said box through pipe 55. On the box a three way distributor 56 also remote controlled by flexible rod 66 and knob provides for the following communications:

(a) In first or discharge position air from outside at atmospheric pressure communicates through canal 6'1 with inside of capsule 45 by channels 5'5 and 60 and through valve 62 described further. In addition the T-shaped passage 68 in the distributor plug sets in communieaton with outside air the inside of box 6 by channel 53, and also the inside of capsule 24 by channel 53 (the branch of T-passage, at right angles with plane of Fig. 6 corresponds with an opening to the outside in downward direction). In this position of distributor 56 shown in Figs. 2 and 6 all parts and enclosures of the apparatus are brought to atmospheric pressure.

(2)) For the purpose of recording an oscillomanogram as will be explained further, distributor 56 is turned or degrees on the left. Communications of outside air with capsule G l and box 6 are sealed. The sole remaining passage for outside air is to inside of capsule 2t through T-hole 68 and a pipe 53.

(c) To record a sphygmogram, an additional quarter turn of distributor 56 is effected on the left. In this position, inside of capsule 2 is connected directly to box 6 by channels 58 and 59 and by the part of T-hole traversing through and through the distributor. All other communications are sealed.

Tube St is extended through valve 62 by channel 61 which is connected to a. single pouch belted armlet of the known type. Or, owing to the fine sensitiveness of my apparatus, the armlet outfit can be advantageously replaced by a simple capsule held by hand on certain arteries giving outside perceptible pulsations such as the temporal or the radial artery.

In all cases armlets (or hand capsules) are in accu ate permanent connection with. inside of. capsule 44. The check valve; 62 (Fig. 7) gives aoneway pas sage. fromv box. 6 to capsule 44.. Surplus pressure box- 6 enters capsule 44 and armlets (or hand capsules) but the reverse does. not occur- Now the. operation of this apparatus is as follows:

In order tov record an oscillomanogram the distributor 53 being. in proper position b, mirror being, suitably adjusted by screws 28 and 49, switching-on the light gives-a brightv spot on left sideof the screen. Armlet is suitably fitted while stop-cock 53 is closed.

is pumped in tank 5i with e. g. a rubber bulb pump fitted onpipe 52'. Pressure is brought.

up to about 40 centimeters of mercury above atmospheric pressure.

In opening stop-cock 53, air pressure rises automatically'and regularly in air tight box. 3 and passing through the discharge valve 62 and capsule 44 rises to the sameextent in armlet pouch.

Inside of capsule 24 remains at atmospheric pressure through T-hole 68 of distributor 56. Rise of pressure in air-tight box li'gradually fiattens down capsule 24 in proportion to the difference of pressures. The downward movement of thecenterof capsule 24 results in a rotation of frame :H and consequently of mirror 5 about the axis of members [2, I3, motion being transmitted through support 23, lever l8, rod l1 and lever 16.

The light spot thus moves on the screen in parallel relationship with the axis of abscissae, in proportion .to rise of pressure in box 6. As pressure rises, arteries and muscles are gradually compressed, the light'spot moving from A to B (Fig. 3). I

When the pressure which prevails in air-tight box 6 and is equal to that in the cuff pouch owing to valve 62, begins to exceed the minimum blood pressure of the patient (diastolic pressure), the arteries are slightly collapsed during the diastolic period, in such a manner that each heart contraction slightly increases arterial beating amplitude with respect to normal state.

Variations in arterial volumes are therefore proportionately transmitted through the armlet and pipes 6|, $53 to capsule 44 in the form of pressure oscillations whatever the frequency of heart beatings may be, as the valve 62 is automatically closed at the very beginning of each pressure oscillation. Capsule 44 is thus sensitive to all variations in the pouch pressure above reference pressure prevailing in box 6.

Every oscillation in pressure is translated as a deformation of capsule 44 which causes the mirror 5 to rotate on shaft l0 through thread 43 and spring 46. Variations in magnitude of arterial beatings under the armlet thus result in Oscillations of the light spot as illustrated by the curve portion BC on Fig. 3, B showing the minimum or diastolic pressure.

As air pressure rises in the armlet, the amplitude of oscillation of the capsule 44 increases and reaches a maximum level (point C on the curve) when the air pressure has reached the mean level of blood pressure. A further rise of pressure in armlet pouch gradually stops all blood circulation by causing blood vessels to be collapsed. Spot oscillations decrease and finally disappear, as there are no more differential manometric variations in capsule 44, (as shown by the curve position DE on Fig. 3).

At point D, the air pressure in the cuff balances the maximum or systolic blood pressure. It being borne in mind that abscissae are proportional to 6v bloodpressureit will; be realized'that the-abscissa ofB, C, D correspond to thediastolic', means and systolic pressures respectively.

For obtaining, a. sphygmogram record, the electric bulb is switched on to cause the light spot to appear on the left sideof the screen, the stopcook 53 is closed and distributor 5.6 placed position previously specified under 0..

In this position, the inside of capsule 24 is communication with air-tight box 6 through channels-58 and 59. Therefore capsule 24 is no longersubjected to deformation due to pressure variations, as inside and outside pressures on said capsule are equal. Then, switching on motor- 40 revolves cam 31, frame ll and spot mirror 5 around axis l2l3 as explained, inv proportion to time.

Uniform rotation of mirror displaces the spot.- in abscissae on the screen, from left to. right. When cam 3| has almost completed its revolu-. tion, the thrust rod 30 rides over a portion 31a: of the cam having a smaller radius, when the spring 33 restores all the levers to initial position- In opening stop-cock 53, compressed air from tank 5|, enters air-tight box 5, armlet and'capsule l4-through discharge valve 62.

As soon as air pressure rises slightly above the minima pressure of the subject stop-cock 53 is closed. (It has been said with reference to Fig. 3 that this occurs when spot oscillations in ordinates suddenly increase in magnitude).

Controls of mirror oscillations on shaft l0 subjected to arterial tension oscillations remain as they were conditioned for oscillomanogram-recording.

In view of the pressure levels in the apparatus enclosures during registration, the displacements of spot in ordinates are in strict correspondence with oscillations of arterial tension. In these conditions, if motor 40 is started, displacement of spot will also take place in abscissae, describing on the screen the sphygmogram shown Fig. 4.

Registration takes place through a single revolution of cams 3|, 36 and 31 (cams 36, 31 controlling contacts 38 and 39). As the mirror is brought back by cam 3| to initial position, light 3 is switched off by cam 36 and contact 38, so there is no spot light allowed to travel on the screen during return course. This switching off can also be replaced by a masking operation, in case switching off and subsequent reheating of the vapour lamp should require too much time.

After one revolution, cam 31 and contact 39 cut oil motor 40, which is always stopped in the same position.

In addition to contact 30 and cam 31 a push button is provided on same Wiring to start the motor 40.

In recording oscillomanograms, lighting of the lamp can readily be actuated by a different switch possibly controlled from knob 6a, closing lamp circuit when the knob is in position b and 0.

While I have described in the foregoing, one embodiment of my invention, I wish it understood that certain departures or various changes may be resorted to, Without departing from the spirit and scope of the invention, so long as the structure falls within the terms of the appended claims.

What I claim is:

1. In an apparatus of the type described to be used in association with a source of fluctuating air pressure, the combination of a frame; a mirror; means providing a Cardan suspension for said mirror in said frame, with allowance for rotation of said mirror about a first axis stationary wlth'r'es'pect to said frame, and about a second axis at right angles to the first axis; means responsive to pressure difierence between the pressure from said source and a reference pressure, for moving said mirror about one of said axes; and means responsive to the pressure difierence between said reference pressure and atmospheric pressure for moving said mirror about the other axis.

- 2. In an apparatus of the type described, the combination of a frame; a mirror-carrier pivotally mounted in said frame for rotation about a stationary axis; a first pressure gauge including a member movable in response to pressure; means operatively interposed between said movable member and said mirror-carrier, for rotating said mirror-carrier; a mirror rotatably supported in said mirror carrier for rotation about an axis at right angles to said stationary axis; a second pressure gauge including a member movable in response to pressure; means providing a flexible connection between said mirror and said movable member of the second pressure gauge, arranged to pass through a point on the first axis, for causing rotation of said mirror about the second axis in response to movement of said second movable member in one direction; and means including a flexible connection between said mirror and said frame, also arranged to pass through said point, for resiliently biassing said mirror to rotation in the direction opposite to that of the rotation caused by the second movable member when the latter moves in the first-named direction.

3. In an apparatus of the type described, the

8? combination of a frame, a mirror-carrier pivotally mounted in said frame for rotation about a stationary axis, a manometric device including an exposed member movable in response to pressure variations in said device, a two-arm rocking lever adapted and arranged to have one arm thereof functionally coupled with said exposed member to move therewith and to be moved thereby, means for coupling the other arm of said lever with said mirror-carrier, so that the rotation of said mirror-carrier is controlled from said lever, a second two-arm rocking lever pivotally supported in said frame, means on one arm of said second lever, providing a pivot and a support for said first lever, and means operatively engaging the other arm of said second lever for rocking said second lever.

FREDERIC ANDRE ETIENNE SERRELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATIENTS 

